Whether a slope is concave, convex, or planar makes some difference
in avalanche danger, usually not a significant difference. Avalanches
happen on any steep slope without thick anchors despite the
shape of the slope. Slope shape makes more difference on smaller
slopes than on larger ones.
slopes statistically produce more avalanches and more avalanche
accidents than other kinds of slopes, partly because they are
inherently less stable and partly because they present more
safe travel problems than other slopes.
slopes have less compressive support at the bottom than other
slopes, which makes a difference for small avalanche paths,
some difference on medium sized avalanche paths but has little
effect of large avalanche paths.
• Convex slopes
tend to wind load more than other slopes. (Wind slows down as
it rounds the convexity which causes it to drop its load of
• Convex slopes are tricky to descend
because each step or turn you take adds another degree of steepness
until suddenly you find yourself on terrain that's too steep.
But you can also use this to your advantage. With a soft slab,
if you descend slowly, especially jumping on the snow or slope-cutting
while you descend, the avalanches tend to break at your feet
instead of above you more so than on planer or concave slopes.
(Remember that hard slabs tend to break above you no matter
• Convex slopes are difficult to assess
because the conditions you find on the upper flat part of the
slope often are much different than on the steepest part of
the slope where you will most likely trigger an avalanche. For
instance, there are a number of stories in which someone digs
a snow profile on the upper section, pronounces the slope safe,
then triggers an avalanche on the steeper part below.
• When descending a convex slopes they are difficult to
exit if you start to find dangerous conditions. You have to
climb back up. All too often people would rather risk their
life by descending than to climb back up.
• Probably the most dangerous shapes are double convexities--convex
vertically and horizontally--like dropping off the edge of a
basketball. These slopes tend to wind-load both from the top
and from the side, they have no compressive support and are
very difficult to descend, ascend or cross safely. If you're
lucky, the wind will erode one side of the slope and wind-load
the other side allowing you to choose the safer eroded side.